Heterogeneously deployed networks with serving node of different nominal transmit powers and (at least partially) overlapping coverage areas are considered to be an interesting future deployment strategy for cellular networks. An introduction to such network deployments can be found in S. Parkvall et al., “Heterogeneous network deployments in LTE”, Ericsson Review, No. 2, 2011, where LTE stands for the Long Term Evolution standard of the 3rd Generation Partnership Project (3GPP).
FIG. 1 illustrates an example of a heterogeneously deployed network 10 with multiple communication devices. Those devices include a low-power serving node 12, a high-power serving node 14 and a wireless communication device 20 that may be served by those serving nodes 12, 14. The low-power serving node 12 (in the following also called “pico node”) typically offers high data rates (Mbit/s) and high capacity (users/m2 or Mbit/s/m2) in local areas where this is needed or desired. On the other hand, the high-power serving node 14 (in the following also called “macro node”) is deployed to provide large-area coverage.
In practice the macro node 14 may correspond to an existing cell 16 (a “macro cell”) of a mobile communication system, while the pico node 12 may be installed later to locally extend at least one of capacity and achievable data rate within the coverage area of the macro cell 16 (where needed). In the exemplary scenario illustrated in FIG. 1, the pico node 12 corresponds to a cell 18 of its own (a “pico cell”). This means that, in addition to downlink and uplink data transmission or reception, the pico node 12 also transmits the full set of common signals and channels typically associated with a cell.
In an exemplary LTE context as illustrated in FIG. 2, the signals and channels transmitted by the LTE-compliant pico node 12 for the wireless communication device 20 served (or to be served) by the pico node 12 include:                Primary and Secondary Synchronization Signals (PSS and SSS), corresponding to the Physical Cell Identity of the pico cell 18.        Cell-specific Reference Signals (CRS), also corresponding to the Physical Cell Identity of the pico cell 18. The CRS may, for example, be used for downlink channel estimation to enable coherent demodulation of downlink transmissions by the wireless communication device 20.        The Physical Broadcast Channel (PBCH), with corresponding pico-cell system information (additional system information may be transmitted on the Physical Downlink Shared Channel, PDSCH).        
As the pico node 12 illustrated in FIG. 2 corresponds to a cell 18 of its own, also so-called Layer 1 (L1) and Layer 2 (L2) control signaling on the Physical Downlink Control Channel (PDCCH) (as well as on the Physical Control Format Indicator Channel, PCFICH, and the Physical Hybrid-ARQ Indicator Channel, PHICH) are transmitted from the pico node 12 to the connected wireless communication device 20. Such L1/L2 control signaling is performed in addition to downlink data transmission on the PDSCH and provides, for example, downlink and uplink scheduling information and Hybrid-ARQ (HARQ)-related information to the wireless communication device 20 within the pico cell 18.
It will be appreciated that similar signals and channels will be transmitted by the macro node 14. The communication between the wireless communication device 20 and the pico node 12 on the one hand and the macro node 14 on the other can occur on the same frequency, or carrier, or on different frequencies, or carriers.
As an alternative to the deployment scenario illustrated in FIG. 2, the wireless communication device 20 in the coverage area of the pico node 12 may be simultaneously connected to the pico node 12 and the macro node 14 as illustrated in FIG. 3. In such a connection scenario, the pico node 12 within the heterogeneous network deployment need not correspond to a cell of its own but may just provide a data-rate or capacity “extension” of the macro cell 16 as shown in FIG. 3. Such a deployment is sometimes also referred to as “soft cell” (or “shared cell”).
In a soft cell deployment as illustrated in FIG. 3, the wireless communication device 20 may maintain a so-called anchor carrier to the macro node 14. The anchor carrier is primarily used for transmitting and receiving control information. Moreover, the wireless communication device 20 may maintain a so-called booster carrier to the pico node 12. The booster carrier is primarily used for transmitting user data.
The wireless communication device 20 may in certain implementations be configured to alternately communicate with the pico node 12 and the macro node 14 in accordance with a communication pattern that comprises communication periods and communication pauses. Such a configuration may, for example, be adopted in a scenario in which the anchor carrier and the booster carrier are deployed on different frequencies while the wireless communication device is configured for single carrier operation.